Exothermic chromium compound containing composition and method of making same



United States Patent EXOTHERMIG CHROMIUM COMPOUND CON- TAINING COMPOSITION AND METHOD OF MAKING SAME Tom S. Perrin and Howard E. Everson, Painesville, and

Harry B. Kinnear, Columbus, Ohio, assignors, by direct and mesne assignments, to Diamond Alkali Company,

Cleveland, Ohio, a corporation of Delaware No Drawing.- Application February 12, 1954 Serial No. 410,042

26 Claims. or; 75-27 This invention relates to a method for recovering chromium metal, and more particularly relates to a method for recovering chromium metal alone or in combination with other metals, such as-a chromium-bearing alloy, and still more particularly relates to the recovery of chromium metal from a mixture of an alkaline earth metal chromate with complex chromium compounds obtained by the reaction of an alkali metal chromate with reducing agents which reduce the chromium to valences apparently intermediate its normal 3 and 6 valent' states, and relates as well to exothermically reacting compositions containing an alkaline earth metal chromate and" the said complex chromium compounds.

In the manufacture of chromium alloy steels, the chromium of the steel may be obtained by dissolving an alloy, such as ferro'chromium, in the molten steel bath. The procedure of dissolving the" alloy in the bath, however, has distinct disadvantages to the steel maker, in

that the time required to dissolve an alloy, such as ferro-.

chromium, in the bath is excessive, during which time there is danger that the bath composition will change. For example, the bath may become contaminated by nitrogen absorbed from the furnace atmosphere, and if an electric arc furnace is used, there is additional likelihood of carbon being absorbed into the bath.

The art, therefore, has sought other means for introducing chromium into alloy baths. One such means is a composition containing a chromium alloy, an oxidizing agent, and a reducing agent comprising slag forming' components. By properly combining the components of such a composition, the exothermic reaction of oxidizing and reducing agents may generate s'ufiicientheat to provide" molten chromium or an alloy thereof in contact with thest'eel hath, whereby rapid solution of'chromi u'mi, or the alloy, in the bath takes place.

Compositions of matter which undergo an exothermic chemical reaction to produce metallic elements and alloys, referred to in the art as exothermic mixes, have in general included as the oxidizing agent, sodium ni- Irate or sodium chlorate, together with a reducing agent, such as silicon, calcium, aluminum, and magnesium, either alone or in the form of an alloy with ferrous or non ferr'o'us metals. Such exothermic mixes have been usedin the manufacture of steel for the purpose of introduc'ing chromium and other metallic elements into a molten steel bath, either in the furnace or in the ladle.

The difficulties encountered in the manufacture of steel with the prior art exothermic mixes containing sodium nitrate includes the introduction of nitrogen into i ECO one or more components of the reducing agent in the form of an alloy, such as commercial grades of ferrochrome silicon (Cr 35-40%, Si 42%-50%)' whereinsilicon is the slag-forming component and the reducing agent. Other metals, such as Ca and A1, may also be included in the form of their alloys, suchas calcium silicide, or ferrochrome silicon aluminunnand thelike, as slag-forming and reducing agent componentsa- The problem faced in the art has beenone of provid-' ing exothermic mixes containing low cost sources of chromium and oxidizing agents which do not produce deleterious gases in the steel bath, while providing areaction sufficiently exothermic that chilling of theste'el' bath is not encountered.

The present invention is based in partupon the finding that complex chromium compounds may be'pro'duced by the reaction of an alkali metal chromate with substances such as hydrogen, carbon, carbonmonoxide; or compounds having hydrogen chemically combined with carbon, ina'non-oxidizing-atmosphere, which compounds are'apparently'in a state of. oxidation intermediate that that of the trivalent and hexavalent forms of chromium: Further, the present invention is based upon the finding that such reaction products will, under proper conditions, react exothermically with certain metal or? metalloid reducing agents to'produce metallic chromium, and

that such reaction is sufficiently exothermic to be useful either in the recovery of chromium metal as such, or in combination with other alloying elements", such; as" in the manufacture of chromium-bearing steel. More= over, since such reaction products are substantially free from sulfur compounds, a'ndmay be produced substan' tially free from'carbon, alloys low in sulfurand-carbon are readily produced in accordance with this invention;

Further, the present invention is based upon the finding that the rate of reaction of such complex" chromium compounds With' certain metal or metalloid' reducing agentsis accelerated and readily' controlled" by the addi'- tion, to a mixture of such materials, of an alkaline earthmetal chromate, for example, calcium chromate, and that such reaction products will, under proper conditions react exothermically with certain metal or niefalloid' reducing agents to produce metallic chromium; and" that such reaction is sufiiciently exothermic and efficient to give unusually high yields of chromium metal, either in the recovery of chromium metal as such, or? in combination with other alloying elements, such as in the manufacture of chromium-bearing steel;

The said complexchromium compounds, upon which the present invention isbased inpart, appear to be a chemical combination of two or more chromium-com taining components which are already saturated accord-'- ing to the classical'concepts of valency; Such complexes are believed to contain chromium in' a valence state intermediate the normal trivalent and hexavalent states of this element, since they may be characterized by (l their ability to yield both trivalent and hexaval'ent chro mium compounds on being calcined at tempe'" turesflof the order of about 980-l000 C., in an oxidizing atmosphere, (2-) their relative chemical inenne'ss except under strong oxidizing conditions, (3) insolubility in water, and (4) other properties which are: not" characteristic of physical mixtures of trivalent and hex-'aval'efit chromium compounds. The present application re lated to application Ser. No; 410,041, filed February 1 2, 1954, in'the name of Tom S: Perrin and-"Howard Everson.

vide exothermic mixes containing an alkaline earth" metal chromate inadmixture with complex chromium: com pounds wherein the chromium is apparently in an intermediate state of oxidation between that 9,15 trivalept and hexavalent chromium, whereby the oxidizing agent of the exothermic mix is used as a source of chromium and contamination by deleterious gases of the metal produced is prevented.

A further object of the invention'is to provide exothermic mixes containing the said complex chromium compoundsmixed withan alkaline earth metal chromate, as the oxidizing agent of such mixes, whereby unusually efiicient and economic recovery of chromiummetal from such mixes is obtained.

Another object of the invention is to provide an exothermic mix from which chromium metal may be, recovered alone or in combination with other metals in an alloy solution.

These and other objects of the invention will be appare ent from the description of the invention given hereinbelow. I I I I I Pursuant to the above objects, the present invention includes exothermic alloying compositions comprising, as

the oxidizing agent thereof, a'mixture of alkaline earth I gen chemically combined with carbon, in a non-oxidizing atmosphere, and comprising as the reducing agent thereof at least one elementfrom the group consisting of alkaline earth metals, Al, and Si. The invention also includes the method of recovering chromium which comprises mixing an alkaline earth metal chromate and a complex chromium compound obtained by the reaction of an alkali metal chromate, in the form of a solid, as opposed to a solution, with a substance selected from the group consisting of hydrogen, carbon, carbon monoxide, and

compounds having hydrogen chemically combined with carbon, in a non-oxidizing atmosphere, with at least one element selected fromthe group consisting of alkaline earth metals, Al, and Si, heating the mixture to effect reaction'between said alkaline earth metal chromate, said reaction product, and an element of said group, and recovering chromium from the reaction products of said mixture. The term alkaline earth metals refers to the group II elements, Mg, Ca, Sr, Ba, and Ra, and the term alkaline earth metal chromates refers to the chromate salts of these metals. The order of preference, both for alkaline earth metals and their chromate salts, in the present invention is Ca, Mg, Sr, Ba, and Ra.

The complex chromium compounds which are prod ucts obtained by the solid-phase reaction of an alkali metal chromate with a substance selected from the group consisting of hydrogen, carbon, carbon monoxide, and compounds having hydrogen chemically combined with carbon, in a non-oxidizing atmosphere, may be obtained from anyone of the alkali metal chromates, such as lithium, sodium, potassium, rubidium, and cesium chromate. Preferably, however, for the purposes of the present invention, such reaction products areobtained by the solidphase reaction of sodium chromate with hydrogen or a compound having hydrogen chemically combined with carbon. These reaction products are preferably obtained at temperatures above 250 C. and below the fusion point of the reaction mass.

Hydrogen, which may be employed in the preparation of the preferred complex reaction products, may be de" rived from any suitable source of hydrogen, such as from the electrolysis of sodium chloride brine or other aqueous solution of an electrolyte. Similarly, the carbon, carbon monoxide, or compounds containing hydrogen chemically combined with carbon may be any suitable material readily entering into reaction with the solid alkali metal chromate, such as, for example, charcoal, graphite, coke, producer gas, coke oven gas, carbohydrates, of which sawdust, wood flour, sugars, starch, and the like are representative, and hydrocarbons, preferably in the gaseous 4 state, of which the lower aliphatic hydrocarbons, both saturated and unsaturated, are representative, may be employed. The solid-phase reaction product of an alkali metal chromate with carbon, or one of the above carbon compounds, may suitably be ,used Where the introduction of carbon into the steel bath is not deleterious. I

The metalloid and metal reducing agents as noted hereinabove, include the alkaline earth metals, Mg, Ca, Sr, Ba, and Ra, as well as Al and Si. These reducing agents, hereinafter referred to'as reductants, may, if desired, be employed alone, but preferably are employed in cornbination with other metallic elements as alloys, and espe cially suitable are those alloys in which silicon is present. Thus, alloys such as the various commercial forms of ferrosilicon, ferrochrome silicon, ferrochrome silicon aluminum, ferrosilicon aluminum (Alsifer), aluminum siiicide, calcium silicide, calcium aluminum silicide, and the like, may be used.

In accordance with the present invention, the'complex chromium compounds referred to. above together with an alkaline earth metal. chromate,preferably calcium chromate, comprise the oxidizing agent of the exothermic mixes. :The proportion of the chromium available from the-alkaline earth'metal chromate' to the chromium available from the complex chromium compounds, in the oxidizing portion of the exothermic mixes, may be varied as desired, but preferably is above about'1:10 and up to 1:3, i. e., the amount of'chromium available from the alkaline earth metal chromate. is preferably substantially above about 56 and up to about /5 that available from the complex chromium compounds.

Where the proportion of chromium from the alkaline earth'metal chromate to the chromium from the com plex chromium compounds is substantially less than 1:10, the combined effect of the accelerated reaction and the control thereof. in a manner to bring about maximunr yields of chromium metaleither as such or as an alloy, is not realized. Also where the proportion of chromium from the alkaline earth metal chromate to the chromium from the complex chromium compounds is substantially greater than 1:3, the exothermic reaction may become sufficiently violent that an appreciable loss of material from the reaction mass is encountered, and appreciably lower recovery of chromium from the exothermic mix may result, especially where calcium chromate is the alkaline earth metal chromate employed and aluminum is used as one of the components of the reductant portion of the exothermic mix.

In order to determine the amount of reductant which may suitably be employed in the compositions and in the practice of the method of the present invention, the oxidizing power of the complex chromium compounds which may conveniently be considered as available for reaction with the above-noted reducing agents, is computed by arbitrarily converting the Cr content of the complex chromium compounds to Cr O and proportioning the calculated amount of oxygen available therefrom to the amounts of the reductants with which it may be combined.

Thus, for example, if a chromium complex material were prepared as described hereinabove, and were found to contain 54.7% Cr (total), this would be the equivalent of 80% Cr O which would be taken (arbitrarily) to represent the portion of the chromium complex material available for oxidizing the reducing agents. If then the significant components of the reductant were Al and Si, for example, it might be desirable to proportion the A] component to the equivalent of all of the alkaline earth metal chromate and /s the Cr O and the Si to the equivalent of /s the Cr O Since the reactions involved for the Cr O may be represented thus:

'5 the computations are conveniently 'set upthus:

with well-known'principles for. calculatingjequivalents in oxidation reductionequations. The amounts of the components' of the reductant indicated' by the computation for the specific alkaline earth metal chromate employed, are also preferably increased by a factor substantially within the range-of 1.1 to 2.5, and'suit'ably by a factor of 1.5 to 1.75.

One reasonfor employing an excess of the reductant over the calculated amount for the complex chromium. compounds arises, inpart, from the fact that the oxygen combined with chromium in the complex chromium compounds is in excess of that required to satisfy the formula cueand the chromium, therefore, as noted above, would appear to be in a valence" state intermediate that of the normal trivalent or hexavalent state, or possibly to be combined with oxygen and alkali metal in some coordinate co-valent state; Another reason arises when silicon is used as one of the. components of the reductant. There is evidence reported in the chemical literature indicating that reaction of' oxygenbearing compoundsand silicon. at high temperatures may result in silicon-oxygencompounds having less than two atoms ofoxygen per atom of silicon.

The higher recovery of chromium where the excess of reductants, as computed above, is of the order of 1.5 to= 1'.T5, would tend' to indicate that the: first of these reasons is sound, and where silicon is on'eco'rnponent of the reductants, that the second reason may also be sound.

In the preparation of the compositions of'the present invention, as. wellas in themethod' thereof; the complex chromium compounds, and the reductants, are preferabl'y in a finely divided'st'ate, and are mixed-together so as toform uniform dispersion of both components. The mixture may be combined with a suitable binding agent and' subjected to'mechanical agglomeration, as by briquettingor pell'eti'zing', or may be usedin' the formof loose, free-flowing powder:

* Where the compositions of the present' invention are employed as ameans ofmakingfinal adjustmentsiin the Example I 100 parts of ingot iron. are placed. in the: crucibleof ahigh frequency. induction fttrnace, and melted. Furnace ,additions .of ,0.25% silicon and. 0.35%. manganesaz. as;

chromium content of'steel in the ladle, suchfcompositions the chromiumin the'exothermic mix.

ferrosilicon and ferromanganese, respectively, are made when the melt reaches the temperature of about 1590 C. Within about /2 minute after the addition of the ferrosilicon and ferromanganese, a sample is poured for chemical analysis. After pouring the base metal sample, the temperature of the metal in the furnace is allowed to rise again to about 1590 C., and the power adjusted to maintain this temperature.

2.2 parts of the reaction product of sodium chromate and gaseous hydrogen, which reaction product, upon analysis, and computing the chromium and sodium content thereof in terms of Cr O and Na O as described hereinabove, gives: Cr O 77.7% and Na O, 13.2%, are dry-mixed with calcium chromate 0.93 part, atomized aluminum 0.70 part, and ferrochrome silicon 1.32 parts, giving 5.15 parts of an exothermic containing 38.8% chromium. The aluminum is proportioned so as to be equivalent to 1.5 times the calcium chromate, plus about 0.5 of the computed Cr O contentof the chromium complex. The silicon is proportioned so as to be equivalent to about 1.2 times the computed Cr O content of the chromium complex.

The temperature of the metal bath in the furnace is increased to about 1760 C., and about /2 of the bath is tapped into a preheated ladle. The 5.15 parts of the exothermic mixture described above are then introduced into the ladle in the form of a loose powder, whereupon the exothermic reaction is initiated and is found to be complete within about /2 minute. The remainder of the metal bath is then tapped into the ladle. The slag produced by the exothermic mix is fluid, and analysis of the bath in the ladle shows that the silicon content thereof, after the addition of the exothermic mixture is 0.34%, and that the chromium content thereof is 1.72%, showing an 87.5% recovery of the chromium in the exothermic mixture. The total amount of all metal recovered from the furnace and ladle is 103 parts.

Example 11 Following essentially the same procedure as that described for Example I above, for the addition of silicon and manganese, a heat is prepared consisting of parts; of ingot iron, which is charged to a high frequency induction furnace. 2.77 parts of the reaction product of sodium chromate and hydrogen, which reaction product, upon analysis, and computing the chromium and sodium contents thereof in terms of Cr O and Na O as in Example 1 above, gives: 70.7% Cr O and 23.4% Na Og are dry mixed with 0.82 part of calcium chromate, 0.39

part of atomized aluminum, and 2.3 parts of ferrochrcme silicon, containing 41% Si, giving 6.27 parts of an exothermic mix containing 40.5% Cr. The aluminum is proportioned so as to be equivalent to 1.5 times the calcium chromate of the exothermic mix, and the silicon of the ferrochrome silicon is proportioned to be equivalent to 1.75 times the computed Cr O content of the chromium complex.

After the temperature of the molten metal bath in the furnace has reached about 1590 C., the furnace is tapped for a sample for analysis, which analysis shows that the bath contains 0.22% of Si, and 0.01% of Cr. The bath in the furnace is heated to a temperature of about 1760 C., and about half of the bath is tapped into a preheated ladle. The 6.3 parts of the exothermic mixture described. above are then introduced into the ladle in the form of a loose powder, whereupon the exothermic reaction is. initiated and is found to be complete within about 1% minutes. The slag formed by the exothermic mix is fairly viscous, at this point, and the remainder of the metal in the furnace is then tapped into the ladle. The metal is separated from the slag, and analysis of the bath in the ladle shows that the silicon content thereof has increased to 0.79%, and the chromium content thereof has increased to 2.53%, giving a 93.2% recoveryof a I F l Example III Following essentially the same procedure as that described for Example 11 above, for the addition of silicon and manganese, a heat is prepared consisting of 200 parts of ingot iron which is charged to a high frequency induction furnace, and sufiicient ferrosilicon and ferromanganese added thereto to provide the same amounts of silicon and manganese as that prescribed in Example II. 11.3 parts of the same chromium complex material as that used in Example II are dry-mixed with 3.15 parts of calcium chromate, 1.5 parts of atomized aluminum, and 8.81 parts of ferrochrome silicon containing 41% Si, giving 24.76 parts of an exothermic mixture containing 40.5% Cr. The aluminum in the exothermic mixture is proportioned so as to be equivalent to 1.5 times the calcium chromate content thereof, and the silicon in the ferrochrome silicon of the exothermic mix is proportioned to be equivalent to about 1.65 times the computed Cr O content of the chromium complex.

After the temperature of the molten metal bath in the furnace has reached 1590 C., the furnace is tapped for a sample for analysis, which analysis shows that the bath contains 0.22% Si and 0.02% Cr. The bath in the furnace is then heated to a temperature of about 1760 C., and about /2 of the bath is tapped into a preheated ladle. The 24.76 parts of the exothermic mix are then added to the ladle in the form of a loose powder, whereupon reaction is initiated and found to be complete within about 1.5 minutes. The remainder of the metal bath is then tapped into the ladle. The slag produced by the exothermic mix is fairly fluid, and analysis of the bath in the ladle shows that the silicon content thereof after the addition of the exothermic mixture is 0.8%, and the chromium content thereof is 4.36%, giving a 94.2% recovery of chromium in the exothermic mix.

Example IV Following the procedure of Example II above, 200 parts of ingot iron, and sufiicient ferrosilicon and ferromanganese to give a 0.25% silicon and 0.35% manganese before the addition of the exothermic mix, are heated in a high frequency induction furnace.

22.6 parts of the reaction product of hydrogen and sodium chromate, prepared as in Example I above, which reaction product, upon analysis, and computing the Cr and Na in terms of Cr O and Na O, as in Example II, gives Cr O 70.7% and Na O 23.6%, are dry-mixed with 6.3 parts of calcium chromate, 3.0 parts of atomized aluminum, and 17.6 parts of ferrochrome silicon to make an exothermic mixture containing 40.5 Cr.

About /2 of the molten metal bath, at about 1760 C. is tapped into a preheated ladle. The exothermic mixturein loose form is then placed on top of the metal. Reaction is initiated substantially immediately and the reaction completed within about 2 minutes, yielding a fluid slag. The remainder of the bath in the furnace is tapped into the ladle. The amount of aluminum added in the exothermic mixture'is proportioned to be equivalent to 1.5 times the calcium chromate present. The amount of silicon added as ferrochrome silicon in the exothermic mix is proportioned to be equivalent to about 1.5 times the computed Cr O of the chromium complex. A sample of the final bath is tapped from the ladle and analyzed. The analysis shows 0.08% carbon, 1.81% silicon, and 9.40% chromium, representing a 96.1% recovery of chromium from the exothermic mixture.

Example V Following the procedure of Example II above, 100 parts of ingot iron, and suflicient ferrosilicon and ferromanganese, to give a 0.25 silicon and 0.35% manga-.

amples II, HI,- and IV above, are dry-mixed with 0.82 part of calcium chromate, 0.38 part of atomized aluminum, and 2.29 parts of ferrochrome silicon containing 41% Si, giving an exothermic mixture containing 40.5 Cr. 7

A sample is tapped from the molten metal in the furnace, and analyzed, and found to contain 0.3% Si, and 0.03% Cr. The temperature of the molten metal bath in the furnace at the time of sampling isabout 1590 C., the metal bath is heated to a temperature of about 1760" C., and about /2 of the bath is tapped into a preheated ladle. The exothermic mixture (6.26 parts) in the form of a loose powder is then placed on top of the molten metal. Reaction is initiated substantially immediately and the reaction is complete within about 1% minutes. The remainder of the bath in the furnace is tapped into the ladle, and the slag is, notedtto be somewhat viscous.

The amount of aluminum in the exothermic mixture is proportioned to beequivalent to about 1.5 times the amount of calcium chromate in the exothermic mix, and the silicon in the ferrochrome silicon is proportioned to be equivalent to about 1.75 times the computed Cr O content of the complex chromium compound.

The metal bath is separated from the slag and a sample of the final bath is tapped from the ladle for analysis. The analysis shows that the silicon content of the metal has increased to 0.69%, and that the chromium content has increased to 2.43%, giving a 98.5% recovery of chromium in the complex chromium compound.

In each of Examples I throughV, the temperature of the metal bath n'ses consistently a minimum of 5060 C., from the time of addition of the exothermic mix to the ladle up to the time when the exothermic reaction is apparently completed.

While there have been described various embodiments of the invention, the methods and products described are not intended to be understood as limiting the scope of the invention as it is realized that changes therewithin are possible and it is further intended that each element recited in any of the following claims is to be understood as referring to all equivalent elements for accomplishing substantially the same results in substantially the same or equivalent manner, it being intended to cover the invention broadly in whatever form its principle may be utilized.

What is claimed is:

1. An exothermic composition comprising as the oxidizing agent thereof, an alkaline earth metal chromate, and the reaction product obtained by the solid-phase reaction, in a nonoxidizing atmosphere, of an alkali metal chromate with a substance selected from the group consisting of hydrogen, carbon, carbon monoxide, and com-,

pounds having hydrogen chemically combined with carbon, said solid-phase reaction taking place at a temperature above 250 C., and below the fusion point of the reaction mass, the chromium of said reaction product being in an intermediate state of oxidation between that of trivalent and hexavalent chromium, and comprising as the reducing agentthereof an element selected from the group consisting of the alkaline earth metals, alumi-' num and silicon.

2. The composition of claim 1 in which said reaction product is the product obtained by the solid-phase reaction of an alkali metal chromate with hydrogen.

3. The composition of claim 1 in which said reaction product is the product obtained by the solid-phase reaction of an alkali metal chromate with carbon.

4. The composition of claim 1 in which said reaction product is the product obtained by the solid-phase reaction of an alkali metal chromate with carbon monoxide.

5. The composition of claim 1 in which the said reaction product is the product obtained by the solid-phase reaction of an alkali metal chromate with a compound having hydrogen chemically combined with carbon.

6. The composition of claim 1 in which said alkali metal chromate is sodium chromate.

7. The composition of claim 6 in which said reaction product is the product obtained by the solid-phase reaction of sodium chromate with hydrogen.

8. The composition of claim 6 in which said reaction product is obtained by the solid-phase reaction of sodium chromate with carbon.

9. The composition of claim 6 in which said reaction product is the product obtained by the solid-phase reaction of sodium chromate with carbon monoxide.

10. The composition of claim 6 in which said reaction product is obtained by the solid-phase reaction of sodium chromate and a compound having hydrogen chemically combined with carbon.

11. The composition of claim 6 in which said alkaline earth metal chromate is calcium chromate.

12. The method of recovering chromium which in- .cludes the steps of mixing an alkaline earth metal chro-' mate, and the reaction product obtained by the solidphase reaction, in a non-oxidizing atmosphere, of an alkali metal chromate and a substance selected from the group consisting of hydrogen, carbon, carbon monoxide, and a compound having hydrogen chemically combined with carbon, said solid-phase reaction taking place at a temperature above 250 C., and below the fusion point of the reaction mass, the chromium of said reaction product being in an intermediate state of oxidation between that of trivalent and hexavalent chromium, with at least one element selected from the group consisting of alkaline earth metals, aluminum, and silicon, and heating the mixture to effect reaction between said alkaline earth metal chromate, said reaction product, and said element of said group.

13. The method of claim 12 in which said reaction product is obtained by the solid-phase reaction of an alkali metal chromate with hydrogen.

14. The method of claim 12 in which said reaction product is obtained by the solid-phase reaction of alkali metal chromate with carbon.

15. The method of claim 12 in which said reaction product is obtained by the solid-phase reaction of an alkali metal chromate with carbon monoxide.

16. The method of claim 12 in which said reaction product is obtained by the solid-phase reaction.

17. The method of claim 12 in which said reaction product is obtained by the solid-phase reaction of alkali metal chromate with a compound having hydrogen chemically combined with carbon.

18. The method of claim 12 in which said alkali metal 10 chromate is sodium chromate, and said alkaline earth metal chromate is calcium chromate.

19. The method of claim 18 in which the material selected from the group consisting of alkaline earth metals,

aluminum and silicon, is equivalent to 1.1 to 2.5 times the sum of the calcium chromate, and the Cr content of said product calculated as Cr O 20. The method of manufacturing a chromium-bearing alloy which includes the steps of reacting, in a non-oxidizing atmosphere, solid sodium chromate with a substance selected from the group consisting of hydrogen, carbon, carbon monoxide, and compounds having hydrogen chemically combined with carbon, at a temperature above about 250 C., and below the fusion point of the reaction mass, the chromium of the reaction product thus obtained being in an intermediate state of oxidation between that of trivalent and hexavalent chromium, mixing said reaction product with an alkaline earth metal chromate, and a non-carbonaceous reducing agent selected from the group consisting of the alkaline earth metals, aluminum and silicon, to form an exothermically reacting mixture, the amount of said reducing agents being within the range of 1.1 to 2.5 times that amount equivalent to the alkaline earth metal chromate and the available oxygen of said reaction product, said available oxygen being computed as Cr O from the total Cr content of said reaction product, combining said exothermically reacting mixture with a molten metal bath with which the chromium is to be alloyed, allowing the reaction between said reaction product and said reducing agents to proceed substantially to completion, and recovering a chromium-bearing alloy from said molten bath.

21. The method of claim 20 in which said alkaline earth metal chromate is calcium chromate.

22. The method of claim 21 in which said reducing agents include silicon.

23. The method of claim 21 in which said reducing agents include an alloy of silicon.

24. The method of claim 23 in which said alloy of silicon is ferrochrome silicon.

25. The method of claim 23 in which said reducing agents include calcium.

26. The method of claim 25 in which said alloy of silicon is calcium silicide.

References Cited in the file of this patent UNITED STATES PATENTS 

1. AN EXOTHERMIC COMPOSITION COMPRISING AS THE OXIDIZING AGENT THEREOF, AN ALKALINE EARTH METAL CHROMATE, AND THE REACTION PRODUCT OBTAINED BY THE SOLID-PHASE REACTION, IN A NONOXIDIZING ATMOSPHERE, OF AN ALKALI METAL CHROMATE WITH A SUBSTANCE SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, CARBON, CARBON MONOXIDE, AND COMPOUNDS HAVING HYDROGEN CHEMICALLY COMBINED WITH CARBON, SAID SOLID-PHASE REACTION TAKING PLACE AT A TEMPERATURE ABOVE 250*C., AND BELOW THE FUSION POINT OF THE REACTION MASS, THE CHROMIUM OF SAID REACTION PRODUCT BEING IN AN INTERMEDIATE STATE OF OXIDATION BETWEEN THAT OF TRIVALENT AND HEXAVALENT CHROMIUM, AND COMPRISING AS THE RECUCING AGENT THEREOF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF THE ALKALINE EARTH METALS, ALUMINUM AND SILICON. 